1. Field of the Invention
This invention relates to shaker pads on nut and fruit tree shakers used in large scale commercial harvesting for shaking tree trunks to dislodge the fruit.
2. Description of the Prior Art
Over the years the agricultural industry has developed equipment which quickly harvests (dislodges) the fruit of entire trees. One type of fruit and nut tree harvester which is applicable to the present invention and which is now widely used has two extending mechanical shaker arms which project outward from the side or front of the harvester. The powered movable shaker arms are designed to part under controllable power and then close to temporarily clamp against the trunk of the tree or on a large limb, whereat the two shaker arms oppose one another on each side of the tree or large branch. The shaker arms are then mechanically vibrated to shake the tree or branch and thus the fruit or nuts out of the tree. Modern tree shakers of this nature are self-propeller drivable vehicles having engines and steering equipment to allow a human operator to ride in the vehicle from tree to tree to shake each tree and dislodge the fruit in an orchard. One example of the many applicable styles of drivable tree trunk shaker harvesters is taught in my U.S. Pat. No. 4,986,065 issued Jan. 22, 1991, which is herein incorporated for essential and non-essential material, primarily for the information pertaining to the self-powered drivable shaker vehicle having two opposing powered shaker arms including shaker pads. The main pads or shaker pads of the harvester of reference U.S. Pat. No. 4,986,065 are single elongated pads horizontally disposed and of a length sufficient to span the tree trunk diameter and wrap substantially around the trunk, as will be further described. It is fastest and thus most economical to apply the shaker arms clamped against the trunk of the tree, thereby eliminating the time consuming process of clamping against individual limbs of the tree to shake individual limbs one at a time. By clamping against the tree trunk, only one clamping and shaking operation is required, and this is much faster than shaking individual limbs. Tree shaking harvesters have been developed and put into wide use which are sufficiently powerful in clamping and shaking ability to be able to grasp a tree trunk and shake the entire tree sufficiently to dislodge essentially all of the fruit or nuts. However, with extremely large and mature trees, such as pecans, pistachios or walnuts for example, tree trunk shakers such as taught in U.S. Pat. No. 4,986,065 are equipped with movable joints and shaker arms which may be elevated, and are applied to individual main limbs of the trees, although the shaker harvesters are in fact designed and built primarily for trunk clamping and shaking. Such trunk clamping and shaking harvesters, because they are structured primarily for clamping against a single relatively large diameter vertically oriented tree trunk, typically include shaker pads which are substantially elongated to span the diameter of the trunk, and are normally cylindrical so that a single elongated pad will be placed lengthwise perpendicularly against a trunk, and when under clamping pressure, deform and wrap about the trunk to a degree. The use of the single substantially elongated shaker pad on trunk shakers is now common place, wherein individual branch shakers typically have included multiple smaller circular pads per shaker head in the past. The use of single elongated shaker pads on each shaker head on modern trunk shakers, as opposed to multiple pivotally attached circular pads as were used in the past, is quite economical. It is less expensive to manufacture a single elongated pad compared to multiple smaller pads. Additionally, it is faster and thus more economical to mount a single elongated pad compared to multiple smaller pads. Additionally, as will be detailed, shaker pads even to this day continue to have significant problems associated with heat build up, and this requires rotation and changing out of the pads, which is clearly much easier with only one large pad per shaker arm compared to multiple pads on a shaker arm. Examples of shaker heads utilizing multiple smaller pads may be examined in U.S. Pat. Nos. 3,479,806 issued Nov. 25, 1969, and 3,596,972 issued Aug. 3, 1971, with the inventor of both of these patents being S. D. Pool. The Pool pads are not structured in a manner which would allow them to be rotated in order to have another side of the pad facing the tree, and this is a major shortcoming since heat will build on the tree facing side to a point of burning or melting the rubbery material unless shaking is performed on a slow basis, shaking few trees per hour, or shaking is periodically stopped to allow the pads to cool down. With modern elongated single pads as discussed above, the pads are loosely retained on the shaker arm by a retaining sling wrapped around the pad, and this loose retention allows the quick and easy manual rotation of the pad within the sling to face a cool side thereof toward the tree. Even if the pads did not get excessively hot, as in the case with the present pads, it is still a good idea to rotate the pads in the retaining sling to apply wear evenly and thus extend the life of the pads, much like that of rotating vehicle tires, and the retention of pads in a retaining sling as is most common today allows for easy rotation compared to bolted-on pads such as in the older Pool patents. However, the Pool pads are relevant to the present invention because they do include a sealed interior chamber having air, or liquid silicone, or air and liquid silicone within the chamber.
Thus, most if not all tree trunk shaker harvesters manufactured today utilize one elongated usually cylindrical shaker pad on each of the opposing shaker heads, with the shaker pad loosely retained in a retaining sling wrapped about the pad and removably bolted to the metal shaker arm. The elongated shaker pads are positioned on the shaker arm in a substantially horizontally disposed position, and this due to the vertical positioning of the tree trunk about which the two opposing shaker pads of the harvester are clamped. It is this type of shaker harvester to which the present invention is applicable. For the purposes of this disclosure, "fruit" includes citrus, plums, prunes, cherries, etc, and any of the many types of nuts which may be dislodged from trees by drivable shaker vehicles. This disclosure is directed toward improved shaker pads disposed between the metal end of the shaker arms and the tree; the pads being utilized to protect the tree and tree bark from being damaged. More particularly, the present invention is an improved substantially elongated shaker pad of the type utilized as a single horizontally disposed pad on each of the two opposing jaws of a drivable trunk shaking harvester.
The shaker heads, as they are commonly referred to in the industry, are the pads and pad retainers on the distal ends of the metal shaker arms. The shaker head of a modern tree trunk shaker normally includes a main shaker pad, a retaining sling, and a slip pad. The shaker pad itself is a relatively large elongated structure as described above, supported on the distal end of the metal shaker arm by the rectangular, somewhat thin flexible pad or sheet referred to as the retaining sling. A second rectangular flexible pad or sheet, commonly known as the slip pad, is attached to the upper surface of the shaker arm and draped downward over the exterior of the retaining sling. The lower or bottom side of the slip pad is releasably attached to the bottom surface of the shaker arm by elastic cords and hooks. The elastic cord attachment method of the slip pad allows the bottom of the pad to be unhooked and flipped upward onto the top of the shaker arm to expose the outer surface of the sling. Exposing the sling allows a heat resistant grease or lubricant to be applied between the sling and the slip pad to decrease the friction between the two pads during shaking. The grease allows the slip pad to remain substantially stationary against the tree while the movement of the vibrating shaker arm, shaker pad and retaining sling is isolated from the tree. Ideally, only vibrational waves or shock waves carry through the outer most layer (slip pad) to the tree so that the bark and delicate cambium layer of the tree is not damaged by movement. Even with the lubricant between the retaining sling and slip pad, friction is still present between the layers of padding and consequently heat is developed. Excessive heat in the main pad, retaining sling and slip pad will cause the deterioration of the padding, and depending upon the degree of heat build up, this can be relatively slow or it can be very quick. Badly deteriorated padding must be replaced due to the development of hard spots and cracks, or proper separation of the movement of the shaker head against the delicate cambium layers of the tree will be lost, leading to trees which die or are stunted. Clearly for understandable economic reasons, it is desirable to replace costly shaker head paddings as little as is possible.
During shaking, the vibrational movement of the main pad, which is under relative high compression, causes heat to be generated internally as the layers of the rubbery pad comprising the main pad rub and move against one another. Even if the main pad were to be made of a single integral piece of rubbery material, thus being absent the typical multiple layers similar to tire construction, the molecules of the single integral piece of rubbery material will be compressed and moved against one another, and thus internal heat will be generated. The main pad is the most expensive, compared to the retaining sling and slip pad. In order to achieve fast and adequate shaking without damaging a tree, a main pad must be reasonably soft so as to assist in not damaging the tree, as the pad is primarily for the purpose of separating the steel end of the shaker arm from the tree, of course vibration must also be transmitted to the tree. The main pad must also be capable of transferring vibration from its side against the metal shaker arm to the outer side which faces a tree. A main pad must be flexible and soft to a degree so as to be able to somewhat deform and wrap about a portion of the tree trunk or branch so that the trunk is somewhat trapped between the two opposing shaker heads, and this so as to be better able to transfer vibration to the tree. It is also desirable that a main pad be highly durable, and again, normally, heat build up is the primary cause of main pad failure.
In the prior art, main pads have been manufactured in various structural forms in attempts to achieve that which is required or desired of a main shaker pad, and all main pads of the past have shortcomings which ultimately lead to higher harvesting costs. Heat build up and durability have been the most significant problems associated with prior art main pads. Other than my liquid circulation cooled pads of my earlier patents which will be listed, prior art main pads have typically fallen into two general catagories. The first being the solid main pad category, and the second being the hollow main pad category. The solid type main pads have been manufactured in elongated rectangular form and cylindrical form. Solid pads, although often having a small diameter central bore lengthwise through the pad to allow some air circulation, are made of thick rubbery material and include no sealed internal chamber. Solid pads although used for many years have now substantially been replaced with what are believed to be improvements thereover, hollow main pads. Solid pads, being very thick walled or completely solid rubbery material develope heat from internal friction relatively quickly because of the large volume of rubbery material rubbing against itself. U.S. Pat. No. 3,335,556 issued Aug. 15, 1967 to J. W. Edgemond, Jr. for "Article Gripping Mechanism" teaches a shaker pad which is essentially a solid pad, although it does include very small interior chambers containing fluid lubricant.
Examples of hollow main pads are shown in U.S. Pat. No. 4,521,468 issued Jun. 4, 1985 to R. W. Brandt, and in U.S. Pat. No. 3,318,629 issued May 9, 1967 to R. W. Brandt, Jr. The Brandt, Jr. patent teaches a thin wall cylindrical main pad having an interior chamber of considerable size compared to the overall pad size. Within the chamber is granular material, such as coarse sand, metal particles or plastic bits. The granular materials are to prevent the pad from becoming collapsed or excessively deformed under the clamping pressures, but also because the granular material is fine and will flow to a degree, to allow for a degree of deformation about the tree trunk so as to allow for good vibrational transmission. U.S. Pat. No. 3,318,629 is herein incorporated by reference primarily for background information pertaining to the structure, use, advantages and disadvantage of hollow main shaker pads filled with granular material.
The Brandt U.S. Pat. No. 4,521,468 teaches a thin walled cylindrical main pad having an interior chamber of considerable size compared to the overall pad size, and one which is quite similar to the pad of U.S. Pat. No. 3,318,629. U.S. Pat. No. 4,521,468 is herein incorporated by reference primarily for background information pertaining to the structure, use, advantages and disadvantages of hollow main shaker pads filled with granular material. The filler or granular material used in the interior of the pads of U.S. Pat. No. 4,521,468 is a dry powder covered plastic rod or chip. The powder on the plastic rods or chips is a lubricant intended to reduce heat build up, and this patent indicates on going research into pad structures for tree shakers, and on going attempts to reduce heat build up.
Other flowable or granular materials which I know have been used as fillers in hollow shaker pads include ground walnut shells, small glass beads, sand of various sizes and plastic beads, all of which has been tried in an unlubricated and lubricated form. However, although hollow granular filled shaker pads generally provide improved deformability and vibration transfer over the solid shaker pads, heat build up remains a costly problem with granular filled pads because the granular material rubs against itself under the clamping and vibrational pressures, and thus generate heat.
As previously stated, problems associated with prior art main shaker pads are primarily durability and maintenance, although vibration transfer, excessive damage to trees, and initial manufacturing costs remain a problem for prior art padding arrangements. Due to continuous heat build up, mostly on the side of the pad facing the tree, prior art pads, whether solid or granular filled, require or would benefit from periodic rotation during harvesting wherein the side facing the tree is manually rotated 180 degree to be facing away from the tree. This rotation is performed every 30 to 60 minutes depending upon the rate or number of trees being shook per hour, and requires the operator to stop the vehicle and get out and manually rotate the pad in the retaining sling. A loss of production occurs each time the harvester is stopped. Additionally, also because of heat build up, the main pads should be temporarily removed and another set of pads placed on the harvester about every two hours, although this time period can vary. The changing of the pads is to allow the used pads to cool down. Although pad rotation and changing is not absolutely required, if one wishes his expensive pads, sling and slip pad to last any appreciable time, rotation and change out of the pads is economically wise with prior art pads even though production is lost when the harvester is shut down.
Even though rotation and changing out of the pads will greatly extend the pad life, and the pad will deteriorate with use mainly due to heat. Also subject to deterioration are the granular fillers used in hollow filled main pads. With the high clamping pressure and vibration, coupled with the build up of heat, the granular material will break into smaller pieces resulting in a less full more crushable pad, and the materials will often begin to clump, as opposed to being a relatively even flowable material (powder). With clumping of the granular materials, the pad begins to get hard spots or areas which will cause damage to a tree. Tree damage can be very expensive when a tree which took 5 to 10 years to grow into a profitable producing tree dies due to damage from a bad shaker pad. When filler clumping occurs, the pad must be removed and the filler taken out of the pad and sifted or replaced. Oftentimes the fillers which seem to function and hold up best are quite expensive, and so it would be desirable for such fillers to last a very long time. Under fast paced modern orchard harvesting with today's modern shakers and hollow filled pads, the granular material often needs to be removed from the pad and sifted or screened, or completely replaced in as few as 8 to 10 shaking hours, and these granular filler maintenance procedures are in the very least costly in terms of labor. In order to lengthen the life of the fillers, the pads can be rotated and changed out more often during the day, and this as mentioned earlier requires the stopping of the harvester and a resultant loss of production.
In attempts to solve the aforementioned shortcomings in prior art shaker pads, I have been experimenting and testing in this field for many years in an effort to provide improved structuring to reduce or eliminate the build up of heat within the shaker pads, retaining slings and slip pads of shaker heads in order to achieve increased durability and higher production in harvesting. One of my earlier inventions was patented on Jul. 19, 1988 under the name "Liquid Cooled Shaker Pad", U.S. Pat. No. 4,757,674. The shaker pad of this patent includes a circulating system of coolant through the main pad, either by gravity, convention or mechanical pump, which is forced or drawn through various channels within the shaker pad. The coolant is circulated through a cooling mechanism exterior of the pad prior to being returned to the pad. The pad of this patent is not a sealed pad, but includes fluid lines extending in and out of the pad, and although this pad structure functions well to reduce or eliminate heat build up in the pad, it is relatively costly to initially manufacture and requires maintenance of the lines and heat exchanger. The coolant lines are also somewhat exposed to possible damage during tree shaking. My U.S. Pat. No. 4,757,674 is herein incorporated by reference for both essential and non-essential material primarily relating to pad structure and use; pad retention on a shaker arm with a retaining sling, for the application of the slip pad on a self-propelled drivable tree shaking harvester, and for the information relating to the problems of heat build up in the shaker head during high speed commercial tree shaking.
Another patent was issued to me on Jan. 16, 1990 entitled "Liquid Cooled Shaker Pad Retaining Sling", U.S. Pat. No. 4,893,458. This invention includes a retaining sling for shaker pads provided with circulatory channels within or between the exterior walls of the pad retaining sling. The sling also has input and output ports and lines which communicate with a fluid circulating apparatus. The sling of this patent is not a sealed sling, but includes fluid lines extending in and out of the sling. My U.S. Pat. No. 4,893,458 is herein incorporated by reference for both essential and non-essential material primarily relating to pad structure and use; pad retention on a shaker arm with a retaining sling, for the application of the slip pad on a self-propelled drivable tree shaking harvester, and for the information relating to the problems of heat build up in the shaker head during high speed commercial tree shaking.
Another patent was issued to me on Jun. 12, 1990 entitled "Method And Apparatus For Cooling The Shaker Heads Of A Tree Shaking Harvester Machine", U.S. Pat. No. 4,932,195. This invention includes a generally closed circulatory system of tubing carrying liquid coolant between a first heat exchanger built into the shaker head and a second heat exchanger located remote of the first one. A coolant is circulated through the system and cools the shaker head. The first heat exchanger may be located in the main pad, the retaining sling or slip pad. My U.S. Pat. No. 4,932,195 is herein incorporated by reference for both essential and non-essential material primarily relating to pad structure and use; pad retention on a shaker arm with a retaining sling, for the application of the slip pad and grease on a drivable self-propelled tree shaking harvester, and for the information relating to the problems of heat build up in the shaker head during high speed commercial tree shaking.
Although the present field is relatively old and crowded, there is still a need for further improvement in the shaker heads of tree trunk shaking harvesters so that overall harvesting costs may be reduced.